package demo2;

class MyCircularQueue {
    private int[] elem;
    private int front;
    private int rear;

    public MyCircularQueue(int k) {
        this.elem = new int[k + 1];
    }

    //入队
    public boolean enQueue(int value) {
        if (isFull()){
            return false;
        }
        elem[rear] = value;
        rear =(rear+1) %elem.length;
        return true;
    }

    //出队
    public boolean deQueue() {
        if (isEmpty()){
            return false;
        }
        front = (front + 1) % elem.length;
        return true;
    }

    //得到对头元素
    public int Front() {
        if (isEmpty()){
            return -1;
        }
        return elem[front];
    }

    //得到队尾元素
    public int Rear() {
        //当rear在0下标，队尾元素是7
        if (isEmpty()){
            return -1;
        }
        //判断在哪
        int index = (rear == 0)? elem.length-1 :rear - 1;
        return elem[index];
    }
    
    public boolean isEmpty() {
        return rear == front;
    }
    
    public boolean isFull() {
        return (rear + 1) % elem.length == front ;
    }

    public static void main(String[] args) {
        MyCircularQueue myCircularQueue = new MyCircularQueue(3);
        myCircularQueue.enQueue(1);
        myCircularQueue.enQueue(2);
        myCircularQueue.enQueue(3);
        myCircularQueue.enQueue(4);
        System.out.println(myCircularQueue.Rear());
        System.out.println(myCircularQueue.isFull());
        System.out.println(myCircularQueue.deQueue());
        System.out.println(myCircularQueue.enQueue(4));
        System.out.println(myCircularQueue.Rear());
    }
}